The piece
Stringer thickness
Which way do they run?
How close together?
The visible gap between one stringer and the next, not centre to centre. to lay them touching.
What you buy
Bullseye stringers are about 17.75 in (451 mm) long, in tubes of 18 in. They are made by hand, so lengths vary slightly — which is why cuts per stringer below is a maximum, not a promise. If your batch runs short, lower this number.
Counts vary by thickness and color, so this is only a rough check on whether one tube covers it. Leave blank if you buy loose.
What you need
How it lays out
Drawn to scale, including the thickness of the stringer itself.
Worth knowing
This counts glass, not technique. It assumes every piece of stringer runs the full way across the glass, and that you cut them from one end of a stringer to the other.
If a run is longer than a single stringer, it says so rather than quietly assuming you will butt two together — that join usually shows.
Stringers are hand made and vary in length, so every count here is a best case. Where the tool suggests a run length to squeeze out an extra cut, it already trims that suggestion back a little so a slightly short stringer does not cost you the cut.